GEOG 1113k Exam 2

What is Desert Pavement and what are the two primary hypotheses for how it forms?

Hypothesis 1: Fines have been eroded by wind and water ("lag") Hypothesis 2: current desert pavement model (Wells and McFadden)

Inselberg

"Island mountain." An isolated surface rising abruptly in a low area.

How much of the conterminous U.S. consists of soluble limestone?

15%

Zone of saturation

2nd zone under the surface. The soil and rock is completely wet and saturated. Its uppermost layer is the water table.

Concrete levees from the flood video were made to withstand how many years of flood action?

500 years

Point bar

A crescent shaped accumulation of sediment along the inside of a meander.

Desert varnish

A dark, shiny coating of iron and magnesium oxides that forms on rock surfaces that have been exposed to desert for a long time.

Playa Lake

A dry lakebed that has small stream flowing into it. Temporary.

Polje

A karst depression that forms a flat plain kind of like a valley, it may hold a stream for drainage or drain into soil.

Erg

A large area covered with loose sand. Most of these deserts accumulated much of their sand during humid periods through deposition in river, lake, or ocean basins.

Natural levees

A low ridge of sediment that builds up on the b.anks of a river, caused by deposition of the coarse portion of the suspended load

Dune

A mound or low hill made up of loose, windblown sand

Hots spring

A pool of water formed by spring that is heated by a magma chamber.

Sinkholes

A rounded depression that is formed by the dissolution of surface carbonate rock. Usually, but not always forms on joint intersections.

Deflation basin

A shallow depression in the ground formed by deflation.

Knickpoint

A sharp irregularity in a stream channel. Ex-cascade, waterfall, rapid.

Poner

A sinkhole forms in a stream and the stream flows down into an underground passage. The streams may reappear later.

Collapse doline

A sinkhole that is formed when a cave or cavern collapses. May have overhanging cliffs and vertical walls.

Rill

A small channel for water to flow through.

Pediment

A surface created by erosion. Extending out from a mountain front. Form as mountains are worn down and eroded back. Fluvial processes are active on lower slopes.

Bornhardt

A type of inselberg made of highly resistant rock that can withstand harsh erosion. The sides are rounded by intense erosion.

Uvala

A valley formed by multiple sinkholes over time.

Yardang

A wind eroded ridge of rock that is elongated parallel to prevailing wind direction.

Permeability

Ability for water to flow through the ground.

Aggradation

Aggradation- The process in which a streambed is raised due to the deposition of sediment.

drainage basin

All of the area that contributes overland flow and groundwater to a particular river or stream. The fundamental landscape unit for collection and distribution of water and sediment.

Rectangular pattern

Alternating bands of tilted hard and soft rocks .Long parallel streams cut into soft rocks. Parallel streams are jointed by short, right-angled segments.

Tower Karst

An advanced stage of karst topography where most of the limestone has been dissolved, the landscape is dominated by tall, steep-sided conical hills of limestone.

Sandplain

An amorphous sheet of sand spread across the landscape

Stream Capture

An event where a portion of the flow of one stream is diverted into another due to natural process.

Aquilude

An impermeable rock layer that is so dense as to exclude water.

Geyser

An underground pool that is heated up by magma. This happens in a small chamber where pressure builds up and leads to an eruption.

Alluvium

Any stream deposited sediment

Mudflow

Are triggered by catastrophic rains, particularly in arid and semiarid settings. Carry large debris. Rains so hard, soil cannot absorb water.

Barchan Dune

Barchan- form trough cross beds with steep dips. Like paw prints

Bedload

Bedload- Large particles carried near the channel floor via hopping, rolling, and sliding.

Braided

Braided- interwoven and interconnected streams, separated by low bars and islands of sand, gravel, and debris. Happens in flat streams with course loads in glacial regions.

Why can limestone be dissolved

Calcite

Explain how water becomes a weak solution of carbonic acid.

Carbon dioxide gas is entrapped and dissolves into the groundwater.

Solifluction

Common in regions containing permafrost. Flows on top of large layers of impermeable bedrock. Usually is a gentle slope.

Shear strength

Composition and thickness of layers and water content

Oxbow lake

Crescent shaped lakes. Once meanders in a stream but the meander was cut off.

Evidence of soil creep?

Curved tress, tension cracks, tilted fences, tilted signs, fallen headstones.

Degradation

Degradation- The process in which the streambed is lowered due to erosion.

Hamada

Desert landscape in which bedrock is exposed. Named after a district of Morocco in the Sahara.

Reg

Desert pavement. A desert surface where all sand and dust has been removed by wind leaving only coarse gravel.

Dissolved load

Dissolved Load- Carried in the form of chemical ions.

Mass Wasting

Downward movement of rock or unconsolidated material due to gravity.

Caolina Bay

Elliptical depressions rimmed with gray or white sand which were eroded during the late Pleistocene.

Flow

Fast and wet wasting. Foothills and mountain bases. Moves as one unit along a curve. Contains large amounts of water.

Slide

Fast wasting that is triggered by rains. Found in areas where joints and fractures exist parallel to the slope.

Fall

Fast, dry wasting. Steep cliffs or mountains triggered by frost wedging.

Salt flat

Filled with "evaporite" minerals that remain on the lake surface after evaporation

Floodplain

Flat area around the stream that floods during over flow.

Artesian Well

Ground water that is forced up from an aquifer due to pressure. Doesn't require artificial pumping.

Solubilty

How easily a rock can be dissolved

Knickpoint migration

Knickpoint migration- The upstream shift of a knickpoint because of erosion. The waterfall is eroded underneath then the tough rock breaks.

Karst

Landforms formed the dissolution of limestone and other soluble rocks, including caves.

Linear dune

Linear- create "herringbone" cross beds, where steeply dipping beds are oriented in different directions. In lines.

Where and how does deposition occur?

Load is carried downstream, deposition occurs on a downward slope.

Local base level

Local base level- controlled by local features such as a larger river or a lake or a resistant bed.

Back swamps

Low, wet, swampy areas in a stream's floodplain.

Meandering

Meandering- a serpentine channel with smooth curves. This type of channel makes loops then abandons them making ox bow lakes. These channels are constantly changing.

Where are some states in which you would find karst topography, e.g., caves, sinks?

Missouri, Florida, Wyoming, Kentucky

Debris flows

Mudflows that contain a large number of rocks and boulders.

Identify the features of a meandering stream.

Ox bow lakes, smooth curves, low gradient, constant changes, and fine bed load.

Paired terrace

Paired- Terraces exist on the same level on each side of the river valley. Usually depositional.

Earthflow

Portion of water saturated land moves a limited downward distance after heavy rainfall. Leaves scars.

River terrace

River Terrace- abandoned floodplains formed when the river flowed at a higher level than at present

Salt wedging

Rock disintegration caused by the crystallization of salts from evaporating water.

Aquifer

Rock or sediment through which groundwater moves easily.

Explain how running water erodes and deposits sediments.

Running water is a very hard force on rock. RW breaks and rubs away rock. The rock and material that is rubbed away is then carried by the water and deposited farther down the stream.

Colluvium

Sediments carried downslope and deposited at the base of slopes. Water isn't involved.

Riffles

Shallow outcroppings of rocks in a channel

Creep

Slow and dry wasting. Down hill. Aided by the alternating expansion and contraction of natural surface.

Yazoo streams

Small streams running parallel to the main stream.

Slope stability

Stability of material

Explain how caverns are formed and the two distinct stages of the formation.

Stage 1: percolating water solves the carbonate bedrock and leaves voids. Stage 2: a "decoration stage" in which ceilings, walls, and floors with a variety of speleothems.

Star dune

Star- cross beds have greatest variety of directions. Shaped like stars.

Cut bank

Steep, retreating bank found on the outside of a meander.

Stream load

Stream Load- All solid matter carried in a stream.

Centripetal

Streams converge into a basin. Coastal.

Radial pattern

Streams drain from a mountain peak or volcano.

Annualar pattern

Streams follow curving courses around resistant rock layers.

Suspended load

Suspended Load- Small particles carried in the water column by turbulent eddies

Porosity

The capacity of the soil to hold water and air.

Talus cones

The cone shaped heaps of talus at the bottom of the rockfall.

Sinuosity

The curving and meandering of a stream. The ration stream length to valley length.

dissolution

The dissolving of rock

Interfluve

The high land above valley sides that separates adjacent valleys

Base level

The lowest level a stream can erode. The imaginary surface extending underneath the continents from sea level at the coasts. Base level isn't exactly flat, it's slightly inclined inland to allow streams some flow.

What is the relationship between increased demand of water supply through development and increased occurrence of sinkholes in Florida?

The more water drained from the water table, the more likely land will cave in.

Dendritic pattern

The most common drainage pattern. It is very leaf-like or tree-like. Underlying structure does not control this pattern. It has nearly horizontal strata

Shear stress

The slopes steepness

Water table

The upper limit of the zone of saturation.

Zone of aeration

Topmost zone within the ground. Rain water percolates down from the surface and the water is in constant fluctuation.

Unpaired terrace

Unpaired- Terrace elevations are different on opposite sides of the river valley, usually due to erosion.

Talus (scree)

Unsorted angular rock that falls in a rockfall. Large rock- talus. Small rock- scree.

What could cause La Conchtia landslides?

Unusual periods of heavy rainfall and periods of dryness.

Vertical accretion

Vertical accretion- A gradual build-up of sediments on the floodplain by multiple flood events, leading to an increase in floodplain elevation.

Lahar

Volcanic mudflow. Fast moving flow of volcanic ash and rock fragment.

Groundwater

Water found in the pores of soil and sediment, plus narrow fractures in bedrock.

Speleothems

When water seeps in to caves it carries calcite and carbon dioxide, this forms speleothems. The Carbon dioxide goes into air and the calcite drips down and hardens to form stalactites. When it drips and hits the floor a stalagmite is created.

Cone of depression

Where the water table has sunk into a shape that is like an inadvertent cone in the immediate area of a well. Happens when a large amount of water is taken out.

Gullies

a relatively deep, vertical-walled channel, recently formed within a valley where no well-defined channel previously existed.

Straight pattern

a short, uncommon channel usually controlled by the underlying geological structure. The stream appears straight but the channel wanders from side to side in the stream.

Trasverse dune

create planar cross beds as straight-crested ripples migrate downwind Like waves on an ocean.

Pools

deep, calm waters in a channel

Absolute base level

sea level

Angle of Repose

the steepest angle that can be assumed by loose fragments on a slope without downslope movement, usually ~ 30-37 degrees.